关键词: 玉米籽粒, 真菌检测, 分离频率, 黄淮海夏玉米区

Abstract:

【Objective】 The objective of this study is to determine the amount of fungi carried in maize grains in Huang-Huai- Hai summer maize region, and to provide reference for safe production, storage, processing and quarantine of maize. 【Method】A total of 720 maize ears were collected at the stages of milk-ripening and full-ripening in 90 cities or counties in 4 provinces (Hebei, Henan, Shandong, Anhui) of the Huang-Huai-Hai summer maize region, 4 full maize ears with no symptom on the surface were sampled in each city or county. All samples were tested for the amount and species of fungi carried, including external and internal tests of maize grains. Washing detection method was used to calculate the spores load on the grain surface, the spore load on the grain surface and isolation rate of each genus were calculated by counting the total number of colonies and dilution multiple. The PDA plate method was used for internal detection. Ten grains tested externally were sterilized and cultured on PDA plate. The fungi carrying rate of grains and the isolation frequency of each genus of fungi were calculated by counting the fungi carrying rate of each grain. In addition, the morphological and molecular identification of the higher frequency fungi were carried out. 【Result】The samples carried a large number of fungi. The spores load of the tested samples ranged from 0 to 1 886 per grain, with an average of 439 spores per grain at milk-ripening stage, the fungi-carrying rate of grains ranged from 0 to 65.0%, with an average of 23.6%. The spores load ranged from 18 to 2 658 per grain, with an average of 942 spores per grain at full-ripening stage, the fungi-carrying rate of grains ranged from 10.0% to 100.0%, with an average of 59.6%. The amount of fungi carried in full-ripening stage was higher than that in milk-ripening stage, but in some areas, the amount of fungi carried was still large in milk-ripening stage. There were differences in the amount of fungi carried in maize grains in different areas. The amount of fungi carried in maize grains in Henan Province was the largest, and Anhui Province had the least amount of fungi, Hebei Province and Shandong Province were in the middle and the difference was not significant. Fungal communities carried both inside and outside of maize grains included Fusarium spp., Penicillium spp., Aspergillus spp., Alternaria spp., Trichoderma spp., Rhizopus spp., Hel-minthosporium spp., Mucor spp. The isolation rate of Fusarium spp. in the grain external and internal detection was 59.1% and 36.1% respectively at milk-ripening stage, indicating that a large number of Fusarium spp. occurred at milk-ripening stage of maize. The isolation rate of Penicillium spp. and Aspergillus spp. in external grains was 8.9% and 0.7% respectively, and the isolation frequency in internal grains was 6.0% and 1.9% respectively, indicating that Penicillium spp. and Aspergillus spp. had begun to infect maize ear at milk-ripening stage. The isolation rate of Fusarium spp. in the grain external and internal detection was 71.9% and 58.5% respectively at full-ripening stage, the isolation rate of Penicillium spp. and Aspergillus spp. in external grains was 17.0% and 0.9% respectively, and the isolation frequency in internal grains was 9.3% and 2.6% respectively, indicating that Fusarium spp., Penicillium spp. and Aspergillus spp. were the main fungi carried by maize grains in Huang-Huai-Hai summer maize region. Morphological and molecular identification results showed that F. verticillioides was the dominant strain in Fusarium spp., the isolation frequency of F. verticillioides, F. proliferatum, F. graminearum was 29.7%, 25.9%, 1.3%, respectively. P. funiculosum and P. oxalicum were the dominant strains in Penicillium spp., and the isolation frequency was 5.0% and 3.6%, respectively. A. flavus and A. niger were the dominant strains in Aspergillus spp., and the isolation frequency was 1.4% and 1.2%, respectively. 【Conclusion】 The maize grains with no surface symptom carried a large number of fungi in both milk-ripening and full-ripening stages, and the amount of fungi carried in the full-ripening stage is higher than that in the milk-ripening stage. Fusarium spp. is the most frequently isolated fungi in Huang-Huai-Hai summer maize region and F. verticilliflora is the dominant strain. It is the dominant pathogen carried by local maize grains.

Key words: maize grain, fungi detection, isolation frequency, Huang-Huai-Hai summer maize region